"Nutrition Substances in Food" Human Nutrition PPT Courseware 5

"Nutrition Substances in Food" Human Nutrition PPT Courseware 5

Please write down two foods you like to eat

(Vegetables, fruits, meat, eggs, milk, etc.)

With the help of the common food ingredient lists on pages 41-42 of the textbook, find out what ingredients are contained in these two foods?

discuss:

1. Do different foods contain the same types and amounts of nutrients?

Answer: Different foods contain different types and amounts of nutrients.

2. Cell life cannot be separated from matter and energy. So, what is the connection between the nutrients in food and the substances contained in human cells?

Answer: Nutrients in food are the source of substances contained in human cells.

1. Carbohydrates, fats and proteins

Carbohydrates, fats and proteins are the main organic compounds that make up cells and can provide energy for life activities.

carbohydrate

effect:

1. The most important energy supply substance for the human body (more than half of the energy consumed by normal life activities of the human body usually comes from sugar);

2. A substance that constitutes cells.

When patients cannot eat normally, they often need intravenous drips of glucose because glucose can provide energy to the body.

Fat

effect:

1. An important substance that provides energy, but is often stored in the body as a backup energy substance.

2. Components that make up cells.

Generally, adults store about 10 to 20% of body mass in fat, which is a backup energy source for maintaining life activities. When a person eats a small amount and the energy in the food intake is not enough to cover the body's consumption, he will consume his own fat to meet the body's needs. At this time, the person will lose weight.

Make assumptions:

Making assumptions needs to be based on existing knowledge and experience. The assumptions made for different questions are different. Some questions may not require assumptions, such as measuring the germination rate of seeds. Before measuring, there is no need to put forward an assumed value for the germination rate of seeds.

hint

The energy in food can be determined by measuring how much heat energy is released when the food is burned.

The food you choose should be easy to burn, such as peanut seeds, walnut seeds, etc.

For every 1 ml of water to rise by 1°C, it needs to absorb 4.2 joules of heat energy.

Experimental steps:

1. In the center of the top of the empty can, cut a round hole slightly larger than the mouth of the conical bottle. Cut several holes around the round hole and around the bottom of the can to facilitate ventilation.

2. Take an Erlenmeyer flask (50 ml), pour 30 ml of water, and put in a thermometer (the lower end of the thermometer should be immersed in water).

3. Refer to the picture on the right to install the experimental device and measure the water temperature.

4. Weigh a dry peanut seed and place the seed on a flame to burn.

5. Place the newly burned peanut seeds at the bottom of the Erlenmeyer flask as soon as possible. After the peanut seeds are completely burned, measure the water temperature.

Think about it:

1. Is it necessary to use empty cans in the experimental device?

2. How can we minimize the loss of energy during the combustion of peanut seeds?

discuss

1. Is your data the same as the data in the appendix on pages 41~42 and the data of your classmates? If different, analyze the possible reasons.

Answer: If they are different, the possible reasons are: the experimental operation is not standardized enough, the measurement is not accurate enough, or there is an error in the calculation, etc.

2. This research experiment is only done once. Is the result reliable? What should be done?

Answer: The research experiment is only done once, and errors may occur, so the results are unreliable. It should be repeated three times with all conditions being the same, and the average of these three times should be taken to minimize the impact of errors.

Exploration experiment

Compare the vitamin C content in different vegetables or fruits

Experimental principle: The aqueous solution of vitamin C can discolor the potassium permanganate solution, and the more concentrated the vitamin C solution, the less the dosage.

Experimental steps

1. Choose any two fresh vegetables or fruits that are commonly eaten locally, put the vegetables or fruits into a mortar and squeeze out the juice or use a juicer to squeeze out the juice. Pour the two juices into two clean, dry small beakers.

2. Take 2 clean, dry small test tubes and inject 2 ml of potassium permanganate solution of the same concentration into each.

3. Take a clean, dry dropper, absorb the first juice, and gradually drip it into a small test tube. While dripping, shaking, and observing, until the potassium permanganate solution loses color, record the juice. number of drops.

4. Refer to the above method, use the above-mentioned dropper to test the second juice, record the number of drops of juice and compare it with the number of drops of the first juice to draw a conclusion.

Note: For accurate comparison, the same dropper should be used for both solutions. Before using this dropper to drop the second juice, you need to wash the dropper with clean water and use absorbent paper to absorb the moisture inside and outside the dropper.

Conclusion: The more drops of juice used, the lower the vitamin C content of the fruit or vegetable; the fewer drops of juice used, the higher the vitamin C content of the fruit or vegetable.

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